Tractor tire



Feb. 4, 1947. J. a. KREYER 2,415,290

' moron TIRE Original Filed March 12, 1945 4 Sheets-Sheet 2(JOHNQKQEYEKDECEASED BYHELEN EKREYERIX :curmx Feb. 4, 1947. I v KREYER2,415,290

TRACTOR TIRE Original Filed March 12, 1945 4 Shasta-Sheet 3 Gay;

nuvnu-rolz d N G.K12EYER, DECEASED BY an iKazvsnz, EXECUTRIX ATTORNEYSFeb. 4, 1947. v J. a. KRE'YER TTTTTTTT RE N V E N T on,

TTTT Ys Patented Feb. 4, 1947 TRACTOR TIRE John G. Kreyer, deceased,late of Akron, Ohio,

by Helen E. Kreyer, executrix, Akron, Ohio', assignor to The FirestoneTire & Rubber Company, Akron, Ohio, a corporation of Ohio Originalapplication March 12, 1945, Serial No. 582,366. Divided and thisapplication October 8, 1946, Serial No. 702,037. In Canada March 11Claims.

This invention relates to pneumatic tires and it refers moreparticularly to tractor tires whose treads have large, deep, widelyspaced traction elements, such, for example, as disclosed in U. S.patents to Clair G. Hoover 2,011,552, James E.

Hale 2,113,527, and William S. Cohen 2,324,996.

Tire tread constructions of this type are used in providing maximumtraction in soft soil operations. In such tread constructions or designsthe traction elements are in the form of bars with the minimum barspacing. being substantially greater than the maximum bar width.Heretofore, tractor tires of' the type described were designed so thatthe surface area of the treads between the traction elements was convexin form. Before the present invention, a tire cavity in a tire mold wasformed in two boring mill operations, one for sweeping out the basecontour of the mold, which is also referred to as the top line, by thosefamiliar with the art. After the plain cavities were swept out, thenecessary recesses, grooves, fillets, etc., for the traction elementswere then engraved or cut intaglio in the second operation,

Tires of the class described, vulcanized in molds used heretofore havenot been entirely satis: factory and have presented serious problems tothe tire industry. Tire engineers and tire production men have soughtdiligently for a solution to certain faults of said tires, which faultsshall be pointed out and discussed hereinafter. However, until thepresent invention, a solution to the problems had not been found.

; Heretofore, that part of the tire ply fabric under the large, deeptraction elements of tires of the said Coben type were lifted or drawntoward the traction elements during the tire molding operation. Also theamount of tread rubber adjacent to the base of said elements wasundesirably thin and the thickness of the tread rubber in the centralarea between said elements was of greater thickness than required ordesired. In cord tires, cord of uneven stretch causes unequal strains onthe fabric cords. Thick rubber between said elements is a waste ofrubber and causes the cords of the tire plies to take improper corddirection by pressing the cord ply stock radially inwardly of the tire.

It was discovered that the concave portion of the tire mold surfacewhich formed or molded the, convex surface of a tire between the largetraction elements actually trapped the rubber therein and did not permitthe necessary flow of rubber from the area between, and removed some-"what from the traction elements to fill that part of the mold cavity inwhich said traction elements .of the mold cavity. This problem wassolved by constructing a tire in which the convexity of the formerlyconvex surfaces between said traction elements was reduced and in someinstances changed to circumferentially substantially flat or concavesurfaces, with corresponding fiat or con vex surfaces in the mold. Thiswas accomplished, as will be understood by those familiar with the art,by radically altering the method of making the tire mold. To make a moldin which a tire embodying the present invention is to be molded, it isnecessary to stop the usual boring mill operation at a point where thereis still enough metal to scrape or otherwise form circumferentially flator convex areas between the traction element recesses of the mold. Theconception of the invention involved a further valuable contribution tothe art,-in that by eliminating the convexity of the surface area, asjust described, a greater depth of cavity between the traction elements:results with no increase in the height of the traction elements. Theload carrying characteristics of any given traction element are notaffected, but the bottom of the grooves defined by said tractionelements of the new tire are removed farther from contact with the roadsurface, thereby providing longer effective life of the tire.

An object of the present invention is to produce a tire of the classdescribed in which the portion of the tread rubber which lies centrallybetween the traction elements is no greater in thickness than adjacentthe edges of said elements.

Another object of the invention is to increase the distance between thecentral portion of the bottom of the groove between tire tractionelements and the top line of said traction elements, thereby providinglonger effective life to the traction elements for a given quantity ofrubber used. Other objects and advantages of the invention will beapparentto those familiar with the art from the following description inconnection with the accompanying drawings wherein:

Fig. 1 is a perspective view of a tire embodying the invention;

Fig. 2 is a plan view of a portion of the tire shown in Fig. 1;

Fig. 3 is a side elevation of a portion of the tire shown in Fig. 1;

Fig. 4 is a. transverse section along line 4-4 of Fig. 2;

Fig. 5 is a. longitudinal section taken along line 5-5 of Fig. 2 andindicating by dotted lines various circumferential contours of thebottom surface of tire tread grooves;

Fig. 6 is a partial circumferential sectional view'taken on line 6-6 ofFig. 2 and illustrating the contour of the surface of the tire betweenthe traction'elements of the tread of a tire embodying the presentinvention, the dotted line indicating the contour of such tires beforethe present invention;

Fig. '7 is the same as Fig. 6 except the contour of the surface of thetire, between the traction elements, is shown as concave rather thanflat as shown in Fig. 6;

Fig. 8 is a fragmentary sectional view of a tire mold in which the tireshown in Fig. 1 was molded;

Fig. 9 is a section taken on line 9-9 of Fig. 8; a d

n F g. is Similar to Fig. 5 and illustrates the misplacement of treadrubber and tire fabric as it occurred in the prior art.

The present application is a division of copending application SerialNo. 582,366, filed March 12, 1945, by John G. Kreyer.

Referring now more particularly to the drawings, in Fig. 1 a, tire 9,having the usual carcass I0, is shown having large, widely spacedtraction elements |2, l3 and I4 defining grooves or cavities l5, I6, I1and I8 therebetween. By reference' to Figs. 4 and 5 it will be seen thatthe surface of the bottoms of the grooves l5 and I6 are arcuate incontour laterally of the tire as best seen in Fig. 4 but, as shown inFig. 5, that the contour of the cavities l5 and I6 are flat or straightin circumferrntial section. It will also be seen by reference to Figs. 4and 5 that the thickness of rubber at the centralarea E of the cavitiesl5 and I6 is no greater than the thickness of rubber adjacent to thebase of the traction elements I I, I2 and I3.

Referring next to Fig. 6 an arcuate dotted line 20 is shown above astraight line 2|. These lines 20 and 2| illustrate the relativecircumferential contour of the bottoms, of the recesses between thetraction elements before and after the pres-- the dotted line 2!!representing 2| representing after the ent invention, before, and theline present invention.

Applicant further found that improvement over the prior art would beobtained if the convex surfaces of the bottoms of the said tread grooveswere changed to circumferentially concave surfaces as indicated by thesolid surface line 22 of Fig. 7. The dotted line 20 of Fig. '7represents the usual circumferential convexity of the bottom of saidgrooves before applicants invention. It will be understood that thebenefits of applicants invention will be progressively approached as thesaid circumferential convexity of the bottoms of said grooves approachesa straight or concave line; however, it has been found that in order tocorrect the faults of tires pointed out hereinabove, the bottoms of saidgrooves should be at least substantially flat or concavecircumferentially of the tire. Fig. 5 further illustrates the inventionby illustrating in one view several of the numerous circumferentialcontours which the surface of the bottom of grooves may have. Contouridentified by line La corresponds to line 2| of Fig. 6, similarly lineLb corresponds to the prior art lines p d generally on 26 of Figs. 6 and'7, and line Ld corresponds to line 22 of Fig. 7. Line Lc indicates acircumferential groove bottom surface contour only slightly flattenedover the prior art. It will now be clear to those familiar with tiredesign that the central portion of said tread grooves identified bylines Lc, La and Ld are in the order just mentioned, closer to the axisof the tire than the central portion of the contour of the prior artidentified by line Lb. The extent to which the bottoms of the treadgrooves will have to be modified over the prior art in the mannerindicated above will dethe volume of rubber which must be molded intothe tread bars and the distance the rubber moves in molding.

In Fig. 8 there is shown a fragmentary sectional view of a tire mold 30of the pot heater type adapted to mold the tire shown in Fig. 1. Saidmold comprises the usual top and bottom halves 3| and 32 respectively.It will be seen, however, by reference to Fig. 9 that instead of thecircumferential contour being the true circle,

heretofore used in tire molds, the present mold has a circumferentialcontour between the traction element cavities of the mold which consistsof many sides, which results from forming circumferentially flat areas Fin the mold between the molds traction element cavities 33, 34, 35 and36. The cavities 33, 34, 35 and 36 of the mold shown in Fig. 8 form thetraction elements I |2, I3 and M respectively of the tire shown inFig. 1. If the bottoms of said recesses |5, |6, i1 and I8 of the tire 9are to have concave circumferential lines such as, for example, as isshown in Fig. 7, then the surfaces of the mold will be correspondinglyconvex, as will be understood by those familiar with the art. The meth-0d of manufacturing tire molds of the form described above has beenbriefly discussed in the first paragraph above and the details of themeth 0d necessary to manufacture such molds will be obvious to thosefamiliar with machine shop practices.

It will now be seen that applicant has produced a tire mold of aconstruction that makes possible for the first time in the art theproper molding of a tire of the type described; that he has increasedthe depth oi the cavities between the traction elements of the treadwithout adversely affecting the stability of said traction elements;

that the present invention for the first time makes possible the moldingof a tire of the type described without the tire ply fabric lifting intotread traction element cavities of the mold, and also the molding ofsuch tire without an undesirable amount of rubber being trapped in thecentral areas of the bottoms of the tread cavities defined by thetraction elements of the tire tread.

By reference to Figs. 5 and 10 it will be seen by comparison that theimprovement in tire construction effected by applicants invention is asubstantial contribution to the art. In Fig. 10, which shows. therelative position of the tread rubber and the fabric plies of tires ofthe type described before the present invention, it will be seen thatthe ply fabric H! at G is lifted or drawn into the base portions of thetraction elements- 6 I2 and II. It will also be seen that there is agreater thickness of tread rubber over the fabric plies at H in Fig. 10than at E of Fig. 5, and that the accumulation of tread rubber at Htogether with the flow or lift of ply stock into the traction elementsresults in a flattened area I on the inside t of the tire.

Modifications may be resorted to without departing from the spirit ofthe invention which is to be limited; therefore, only by the prior artand the scope of the appended claims.

What is claimed is:

1. A pneumatic tire for use on motor vehicles adapted to operate on andof! the road, said tire comprising a flexible casing having a treadportion formed integrally with transverse traction elements arranged incircumferentially spaced series thereon, said traction elementscomprising upstanding lugs, which lugs define recesses therebetween ofgreater transverse width than the width of the lugs, the bottoms of saidrecessesbeing straight circumferentially of the tire, as viewed in sideelevation.

2. A pneumatic tire of the character described, said tire comprising aflexible casing having a tread portion formed integrally with transversetraction elements arranged in circumferential series thereon, saidtraction elements comprising spaced upstanding lugs, which lugs definerecesses therebetween wider transversely than the widththerebetween ofgreater transverse dimensions than the base of the elements, the radiusof the the at the surface of the bottom of the'central portion of eachrecess being a distance less than the length of the radius of the tireat the base of said lugs, measured in a plane at right angles to theaxisof the tire.

of said lugs, the bottoms of said recesses being A concave inlongitudinal section of the tire, said concavity being defined inlongitudinal section by a circumferential section of a circle, thecenter of which is disposed exteriorly of said tire.

3. A pneumatice tire of the type having tread bars spaced at a greaterdistance than the bar width, comprising a casing having a tread portion,said tread portion having two series of traction elements in the form ofoutwardly projecting,

laterally extending, elongated lugs arranged successively incircumferentially spaced relation with the lugs of the same series anddefining grooves between said lugs, the width of said grooves at theirnarrowest point being greater than the width of said lugs at theirwidest portion and the thickness of the tread rubber at the central areaof the bottom of a groove being no greater than the thickness of thetreadrubber at the base of the lugs defining said groove.

4. A pneumatic tire of the character described,

thickness of the tread rubber at the base of the lugs defining saidgroove.

5. A pneumatic tire of the character described. comprising a casinghaving a tread portion, said tread portion having two series of tractionelements in the form of outwardly projecting, laterally extending,elongated lugs, arranged successively in circumferentially spacedrelation with the lugs of the same series and defining grooves betweensaid lugs, the width of said grooves at their narrowest point beinggreater than the width of said lugs. at the widest point thereof and thebottom of said grooves being straight oircumferentially of the tire, asviewed in side elevation.

6. A pneumatic tire of the traction-type described, comprising a casinghaving a tread portion, said tread portion having two series of tractionelements in the form of radially outwardly projecting, laterallyextending, elongated lugs, arranged successively in circumferentiallyspaced relation with the lugs of the same series and defining groovesbetween said lugs, the width of apices of the polygon.

8. A pneumatic traction tire of the character described, comprising acasing and a tread portion integral therewith, said tread portioncomprising a plurality of elongated lugs disposed laterally of the tireand in circumferentially spaced relation, at distances greater than thewidth of said lugs to provide intervening grooves, said grooves havingbottom wall portions which are convex laterally of the tire but straightin longitudinal sections thereof.

9. A tire of the class described having spaced traction lugs definingtread grooves therebetween: the minimum width of said grooves beinggreater than the maximum width of said lugs, the surface at any point inthe central portion ofsaid grooves being spaced a distance from the axisof the tire less than the distance from said axis to the base of saidlugs, measured in a plane at right angles to the axis of the tire.

10. A pneumatic tire comprising a fiexilble casing having a treadportion formed integrally therewith and including circumferentiallyspaced transversely extending tread bars defining recesses therebetween,said recesses being wider transversely thereof, at their narrowestwidth, than the greatest transverse bar width, the surfaces of saidrecesses being continuously concave between the tread bars in adirection circumferentially of the tire.

' 11. A tire including a tread portion comprising a plurality ofelongated lug bars disposed to extend laterally of the tire and incircumferentially spaced relation to define grooves the minimumtransverse dimensions of which are greater than the maximum bar width,with bottom surfaces of said grooves presenting a straight sidedpolygonal configuration in any longitudinal section of the tire, withthe lug bars integrally 'joined at the HELEN E. KREYER, Emecutriw of theEstate of John G. Kreyer, De-

ceased.

REFERENCES orran The following references are of record in the file ofthis patent:

